Part vi:i: su>imary and conclusions 



68. Numerical hydrodynamic models were developed anc tested for the 

 purposes of evaluating the influence of proposed structures under storm con- 

 ditions and providing elevation and velocity data for concurrent numerical 

 sediment transport studies at Oregon Inlet, North Carolina. Data collected 

 for previous physical model studies were supplemented by additional data from 

 NCAA and unpublished SAW letter reports for use in calibrating and verifying 

 rh2 models under existing tidal conditions and for two severe storms of 

 record — the March 1962 northeaster and Hurricane Donna (1960). Three nodels 

 with progressively finer resolution (offshore, nearshore, and shore process) 

 were successfully calibrated (relative to their respective degree of resolu- 

 tion) to replicate an astronomical tidal event. Using a tuned hurricane 

 windfield model for Donna and windfields developed by the Wave Information 

 Study at WES for the March 1962 storm as forcing parameters, the models were 

 able to duplicate observed marigrams throughout the model area. Observed bay- 

 ocean head differentials also were modeled correctly, particularly the 20-hr 

 plus flood event through Oregon Inlet during the peak of the Marrh 1962 storm. 



•59. Tv'o structural alternatives (n'nvolving parallel jetties with 

 2,500- and 5, OOO-f t-wide spacings) were studied under tidal and storm condi- 

 tions. Structural effects were determined to be limited to the inlet under 

 tidal conditions and to the immediate inlet vicinity under ci»;cumstances 

 approximating Hurricane Don.;a. The maximum possible influence exerted by any 

 changes at the inlet was determined by simulations with the inlet completely 

 closed (this was not actually a proposed improvement pirn) uader Hurricane 

 Donna conditions. For this case, no change was noted beyond a 12-mile radial 

 distance from the inlet. During Hurricane Donna, peak surge levels at the Pea 

 Island Coast Guard Station and the Oregon Inlet Marina were increased by 2.4 ft 

 and 1.4 ft, respectively, with total closure of Oregon Inlet. These stations 

 are in the Immediate inlet vicinity (within a 1.2-inile radius). For the 

 2,500- and 5,000-ft spacings, peak surge level increases for the nearby sta- 

 tions mentioned above were even smaller, with little or no differences noted 

 at farther distances from the inlet. 



70. Finally, simulations at very fine grid resolutions were made to 

 provide hydiodynamic data for the sediment transport studies covering the 

 normal range of tides with no jetties, for four structural alternatives with 

 a miian tide, and for the historical March 1962 northeaster with no .iettlcs. 



45 



